# TDF and Portability

### January 1998

1 - Introduction
2 - Portability
3 - TDF
4 - Conclusions

# 1. Introduction

TDF is the name of the technology developed at DRA which has been adopted by the Open Software Foundation (OSF), Unix System Laboratories (USL), the European Community's Esprit Programme and others as their Architecture Neutral Distribution Format (ANDF). To date much of the discussion surrounding it has centred on the question, "How do you distribute portable software?". This paper concentrates on the more difficult question, "How do you write portable software in the first place?" and shows how TDF can be a valuable tool to aid the writing of portable software. Most of the discussion centres on programs written in C and is Unix specific. This is because most of the experience of TDF to date has been in connection with C in a Unix environment, and not because of any inbuilt bias in TDF.

It is assumed that the reader is familiar with the ANDF concept (although not necessarily with the details of TDF), and with the problems involved in writing portable C code.

The discussion is divided into two sections. Firstly some of the problems involved in writing portable programs are considered. The intention is not only to catalogue what these problems are, but to introduce ways of looking at them which will be important in the second section. This deals with the TDF approach to portability.

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